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Powerwall charge rate limited to (10kW - home load) during storm watch

nickID

Member
Dec 16, 2018
159
199
US
I'm trying to figure out why my three Powerwall 2 system is limiting the Powerwall charge rate to 10kW minus the current home load, when charging from the grid during Storm Watch. The three Powerwalls should be able to charge at 15kW continuous. And my home can pull more than 10kW from the grid, so the limitation is not there. My inverter is 10kW, so my max charge rate from solar is 10kW, but I didn't think that should limit the rate from grid->powerwall. Any ideas?

upload_2021-2-12_17-34-7.png
 

wjgjr

Active Member
May 11, 2020
1,160
896
Silver Spring, MD
I believe this is the standard behavior - about 3.3 kW per PW. I have seen this with my 2 PW system. That said, I would not have expected it to subtract out the home load - that may be a system bug.
 
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miimura

Well-Known Member
Aug 21, 2013
6,161
5,753
Los Altos, CA
That doesn't match my experience. During Storm Watch, the Powerwalls should charge at 3.3kW per Powerwall. I have two, so the total charge rate is 6.6-6.7kW. If you have three, they should charge at 10kW and the grid draw should be the sum of the Home and Powerwall figures. Example chart showing the fixed power charging and varying grid draw. You will also notice that the solar contributes and reduces the grid draw. You will also notice that I turned off Storm Watch and let the solar continue to top off the Powerwalls.

Chart 2020-08-16.jpg
 
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nickID

Member
Dec 16, 2018
159
199
US
Thanks to you both for confirming that 3.3kW per PW is correct. After rechecking the data sheet, I see that line now (max 3.3kW charge from the grid).

I will have to figure out why they aren’t pulling a full 10kW in my system.
 

gpez

Member
Apr 25, 2019
652
530
USA
Thanks to you both for confirming that 3.3kW per PW is correct. After rechecking the data sheet, I see that line now (max 3.3kW charge from the grid).

I will have to figure out why they aren’t pulling a full 10kW in my system.

Can you share a graph with your house draw and Powerwall draw? I'm curious if the total of the two always is 10kW. If your house is pulling 10kW or more does the Powerwall stop charging?

If both are true I wonder if there is a Tesla side config setting that does this and is set for you (maybe by accident?).
 

nickID

Member
Dec 16, 2018
159
199
US
Can you share a graph with your house draw and Powerwall draw? I'm curious if the total of the two always is 10kW. If your house is pulling 10kW or more does the Powerwall stop charging?

If both are true I wonder if there is a Tesla side config setting that does this and is set for you (maybe by accident?).

Good idea. Interesting result: when my home use was higher than 10kW yesterday (while storm watch was enabled), not only did the PWs stop charging, they actually covered the demand in excess of 10kW. I’ve had no trouble pulling greater than 10kW from the grid in the past, for example when the power walls are empty or at the backup minimum value. There must be something funky in my config for storm watch.

I reached out to Tesla yesterday; I’ll report back once I hear from them.
upload_2021-2-13_12-1-4.png
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,377
2,486
Northern California
I'm trying to figure out why my three Powerwall 2 system is limiting the Powerwall charge rate to 10kW minus the current home load, when charging from the grid during Storm Watch. The three Powerwalls should be able to charge at 15kW continuous. And my home can pull more than 10kW from the grid, so the limitation is not there. My inverter is 10kW, so my max charge rate from solar is 10kW, but I didn't think that should limit the rate from grid->powerwall. Any ideas?

View attachment 636233
What we can't see and I did not notice in your responses is what the SoC is on your PWs. If they were near full then this would be acceptable. If below about 90% full then not.
 

gpez

Member
Apr 25, 2019
652
530
USA
Good idea. Interesting result: when my home use was higher than 10kW yesterday (while storm watch was enabled), not only did the PWs stop charging, they actually covered the demand in excess of 10kW. I’ve had no trouble pulling greater than 10kW from the grid in the past, for example when the power walls are empty or at the backup minimum value. There must be something funky in my config for storm watch.

I reached out to Tesla yesterday; I’ll report back once I hear from them.
View attachment 636454

Sounds like maybe a Grid Import Limit is set to 10kW. Tesla should be able to figure out what's up from their end.

I haven't poked at the installer UI but it is also possible there's an option there...
 
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miimura

Well-Known Member
Aug 21, 2013
6,161
5,753
Los Altos, CA
Sounds like maybe a Grid Import Limit is set to 10kW. Tesla should be able to figure out what's up from their end.

I haven't poked at the installer UI but it is also possible there's an option there...
The behavior shown is consistent with this conclusion. However, I can't imagine why it would be set that way. 10kW is only 42A at 240V. That is a strangely low limit for the grid import.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,113
8,972
Riverside Co. CA
The behavior shown is consistent with this conclusion. However, I can't imagine why it would be set that way. 10kW is only 42A at 240V. That is a strangely low limit for the grid import.

It seems like it would be a strangely low limit, yeah. I mean, my Tesla wall connector on a 60amp 240v circuit pulls more than that when my car is charging.
 

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